I'm trying to apply a patch to my repo, darcs says I'm missing a patch.
darcs changes --patch <name> show's I do indeed already have the "missing" patch.

Patch created and trying to apply with
$ darcs -v
2.2.1 (release)

Trying to apply:
$ darcs apply A\ forwarded\ darcs\ patch.eml 
darcs: Cannot apply this patch bundle, since we're missing:
Sun Feb 11 10:29:59 CET 2007  
Lennart Kolmodin <kolmodin@dtek.chalmers.se>
  * Add darcs-monitor

Shouldn't I have that patch already? Indeed I do.
$ darcs changes --patch "Add darcs-monitor"
Sun Feb 11 10:29:59 CET 2007  Lennart Kolmodin <kolmodin@dtek.chalmers.se>
  * Add darcs-monitor

Missing any patches from the repo?
$ darcs pull
Pulling from "code.haskell.org:/srv/code/gentoo/gentoo-haskell"...
gentoo-haskell MOTD
**********************
No remote changes to pull in!

Broken repo?
$ darcs repair
The repository is already consistent, no changes made.

Rolled a tarball for the repo, turned out to be quite big.
Put it here (70mb):
http://haskell.org/~kolmodin/issue-1399-gentoo-haskell-apply.tar.gz

Looks like the .eml patch got mangled by the email client (thunderbird).
It works if I manually remove a newline between the two rows in the patch:
[Add darcs-monitor

Lennart Kolmodin <kolmodin@dtek.chalmers.se>**20070211092959] =

It's unlikely due to darcs, I'd guess. Mark as not-our-bug?

Thanks. We are not crystal clear on the use of priorities and status codes, but 
I have marked it not-our-bug for now, as you suggest. But furthermore, I am 
thinking that it should be possible for darcs to report this sort of thing in a 
more useful manner, so I will leave the issue in status chatting for now.

Best regards
Thorkil

I think we can treat this as essentially a documentation problem resolved with
this FAQ entry:

http://wiki.darcs.net/Troubleshooting#patches-falsely-reported-as-missing